1. Field of the Invention
The invention relates generally to length-adjustable shafts or poles, for use in a variety of applications, including golf clubs, light stands, music stands, camera tripods, walking sticks, canes, shower curtain rods, ski poles, cleaning implements, and extendible tools. More specifically, the invention pertains to an adjustable length shaft having an internal locking mechanism with teeth and accommodating teeth recesses, the teeth and recesses providing a plurality of positive locking positions, each position providing a different shaft length.
2. Description of the Prior Art
Prior art shafts having adjustable lengths, have been used for many years for a wide variety of applications. Each of these applications has its own functional and aesthetic requirements for the shaft construction which is employed. As a consequence, a number of different mechanisms have been developed to satisfy the particular application requirements.
For example, a telescopic shaft arrangement using a rotatable nut and a compression ring locking mechanism, has been very popular for light duty camera tripods, walking sticks, canes, and extendable poles. An even simpler construction, using a telescopic shaft in combination with a transverse set screw or bolt for compressively locking the shaft, has been used successfully for certain non-demanding applications such as support shafts for music stands and lighting stands. Stronger adjustable length shafts, using a telescopic square tube construction with a flip lever compression lock, have also been developed. These stronger shafts are used for heavier duty tripods, and other applications where the ability to withstand greater axial forces is important. Lastly, a rod construction including a screw-extensible threaded shaft, having a disc foot on its exposed end, has been used for many years as an adjustable support rod for shower curtains.
The above-described prior art constructions have not been used successfully for a number of other demanding applications which could benefit from appropriately featured adjustable length shafts. One of these applications is for adjustable length golf clubs. The reasons are several. Golf clubs must be clean in construction and appearance, to satisfy the consumers"" aesthetic requirements. Consequently, flip levers, set screws, and even compression ring mechanisms are not well received for this application. In short, the adjustable length golf club shaft must look substantially identical to a standard fixed length golf club shaft, to be acceptable.
Also, an adjustable length shaft for a golf club must have the same feel as a fixed length shaft, even to be considered by the golfing community. Golfers are notoriously critical and demanding, particularly when it comes to their equipment, so an adjustable shaft that exhibited looseness, lateral play or axial slippage of any sort, would simply be unacceptable.
And, an adjustable length shaft in this application must be both fast and easy to adjust, and positive in its locking capabilities, to be acceptable for golfers. Similar requirements exist for adjustable ski poles, both as to aesthetic and functional aspects.
Thus, the need exists for an improved adjustable shaft construction, which can be used in a variety of fields, and will also satisfy the demanding criteria for golf club and ski pole applications.
The adjustable-length shaft assembly of the present invention includes a handle and an elongated shaft. The shaft has an upper portion which extends axially within the handle, and is axially adjustable for locking therein. The shaft includes a tooth plate at its upper end. Preferably, two sets of teeth extend from the plate, one on each side of the plate, for more balanced distribution of locking forces and for additional strength. If the shaft assembly is to be used as part of a golf club, a club head is mounted on the lower end of the elongated shaft. For other applications, different articles or other structures may be attached to the shaft or to the handle portion of the assembly.
An elongated, tubular, inner sleeve is located within the handle, surrounding the upper portion of the shaft. The sidewall of the inner sleeve includes upper and lower pairs of cam surfaces, on opposing sides of the inner sleeve. The sidewall cam surfaces resemble a dog-leg, or a dual angled slot, in configuration. These cam surfaces progress from a lower left-hand end upwardly to an upper right-hand end. The inner sleeve also includes an angled cam surface at its lower end. The lower end cam surface extends on a straight angle, from an upper left-hand position downwardly toward a lower right-hand position. A pin detent is provided adjacent the lower right-hand position.
Lastly, the inner sleeve includes a pair of opposing longitudinal tooth plate slots, each approximately 90 degrees rotated from the sidewall cams, and extending generally the same distance between them. The longitudinal plate slots accommodate both sides of the tooth plate, so as to allow sliding of the plate and axial adjustment of the shaft within the inner sleeve. However, the sides of the longitudinal slots restrict any rotational movement of the shaft, relative to the sleeve.
The handle portion of the shaft assembly also includes a tubular housing, positioned about the inner sleeve. The housing is comprised of a left hand shell and a right hand shell. Each shell includes upper and lower cam followers which engage a respective sidewall cam surface of the inner sleeve. Each shell further includes an elongated tooth slot in its sidewall portion. Each tooth slot has a tooth rack extending along one side. The tooth slots have a transverse dimension which is sufficient to accommodate sliding of the tooth plate when it is rotated into an unlocked position.
A tubular outer sleeve is also provided around the housing. The outer sleeve includes sidewall recesses which are engaged by locking fingers, extending slightly outwardly from the sidewalls of each of the shells of the housing. In this way, the outer sleeve acts to hold the two shells together, and to prevent them from rotating.
A blocking pin is transversely positioned across the upper ends of the outer sleeve and the housing. Holes are provided in the sidewalls of the outer sleeve and the housing for securing the pin in place. A cam-bias spring is located within the upper end of the housing. The spring is captive between the upper end of the inner sleeve and the blocking pin, providing a downward bias force against the inner sleeve.
A tubular control handle is located about the lower portion of the outer sleeve. The control handle includes a cam pin extending inwardly toward the inner sleeve, passing first through a transverse cutout in the lower end of said outer sleeve and then through a housing cam in the lower end of the housing. The cam pin thereby engages the angled cam surface at the lower end of the inner sleeve. The cam pin detent at the lower end of the angled cam surface secures the cam pin and the control handle in an unlocked position, so the shaft can be axially adjusted to set the proper length for the shaft assembly.
Upper and lower plastic brake rings surround a lower portion of the shaft, within the confines of the control handle. The brake rings include partial gaps in their sidewalls, so that axial forces applied to the end of either brake causes the ring to compress radially upon the shaft and lock it in place. The upper end of the upper brake ring impinges upon the lower edge of the housing. The lower end of the lower brake ring nests against an annular, angled wall of the control handle. A brake spring between the two rings maintains them in spaced relation, and transmits axial forces between the upper ring and the lower ring.
To change the effective length of the shaft assembly, the control handle is rotated in a clockwise direction, in relation to the outer sleeve and the housing. This moves the cam pin along the angled cam surface of the inner sleeve and along the housing cam surace. This urges the inner sleeve upwardly, causing the upper cam surface of the inner sleeve to rotate the inner sleeve and the teeth on the end of the shaft, away from the housing and the teeth rack. The spring at the upper end of the housing becomes increasingly compressed. Continued clockwise rotation causes the teeth and the tooth rack entirely to disengage, as the cam pin engages the cam pin detent in the inner sleeve. Concurrently, the cam pin moving against the downwardly directed housing cam surface urges the control handle downwardly with respect to the lower end of the handle. This releases compressive forces on the brake spring and axial forces on the brake rings, thereby freeing the shaft. The shaft may now be moved axially, upwardly or downwardly, until the shaft assembly assumes the desired overall length.
To lock the shaft assembly, the control handle is rotated counter-clockwise in relation to the outer sleeve and the housing. As the cam pin disengages from the detent, the angled surface of the inner sleeve, under downward forces from the cam-bias spring at the upper end of the housing, begins to move downwardly in relation to the housing. Under this downward motion, the upper and lower cam surfaces of the inner sleeve in conjunction with the cam followers on the housing, cause the teeth protruding from the inner sleeve to rotate toward the tooth rack on the housing. As rotation of the control handle continues, the teeth mesh with the tooth rack, locking the shaft against axial movement. Concurrently, the cam pin moving against the upwardly directed housing cam surface, moves the control handle upwardly. This compresses the brake spring, imposing greater axial forces on the brake rings. The brake rings compress on the shaft, further preventing axial or lateral movement of the shaft. A locking detent in the extreme counter-clockwise end of the housing cam surface locks the cam pin securely in place.